The present invention relates generally to the field of corrugated boards, and more particularly, to a low friction machine for manufacturing corrugated board by emitting bursts of air from pressure applicator.
Manufacturing corrugated board generally involves creating corrugations or ridges in a median. Positioning the corrugated median between flat liners can form a board of desired thickness. An adhesive between the median layer and substantially flat liner layers secures the median to the liners. Typically, this positioning involves placing the board along a raceway of an assembly line. The assembly line often includes a hotplate section, cooling section, and scoring section.
The hotplate section includes a heat source, typically a series of steam chests that remove moisture and set the adhesive by heating the board. A pressure applicator presses the board against the steam chest to ensure adhesion across the entire width of the board and prevent blisters from forming in the board. Because repeated pressure on the steam chests can cause sagging in the middle, some corrugated board machines use multi-foot pressure applicators that apply variable pressure across the width of a steam chest.
Typically, a conveyor belt in the hotplate section propels the board along the assembly line. The board is typically positioned between the steam chests and the conveyor belt. Positioning the pressure applicators above the conveyor belt can cause direct contact between them and the conveyor belt. Consequently, the conveyor belt translates the pressure from the pressure applicators to the board. Thus, the sliding contact between the conveyor belt and the pressure applicators creates considerable friction.
The resulting friction between the pressure applicators and the conveyor belt causes considerable wear to both the feet and the belt. These parts, which are quite expensive and difficult to replace, therefore warrant frequent replacement. Worse yet, replacing these parts is a major maintenance event that results in shutting-down the entire assembly for an extended period. This is expensive, not only in terms of the cost of the parts, but also in terms of down time. There is, therefore, a need to maximize the life of the pressure applicators and the conveyor belt.
Previous solutions attempted to minimize friction between the belt and pressure applicators in a variety of ways. One solution added a low-friction coating, such as polished steel, TEFLON, or ceramic coatings to the pressure-applying feet. While use of this coating reduces the wear to both the feet and the conveyor belt, it does not solve the problem. Eventually the coatings wear off and the friction problem reoccurs. Other solutions include covering the pressure applicators with a low friction material. Like the coating solution, the covers eventually wear off and the pressure applicators have to be replaced.
Another conventional solution removes the conveyor belt from the hotplate section of the assembly line. Some other conveying mechanisms, such as a pulling section located downstream from the hotplate section, can propel the board through the assembly line. Although wear to the conveyor belt is eliminated, there are a number of problems with this approach. First, the pressure applicators still wear. Second, it may be desirable to change the thickness of the board, by adding or removing adhering layers, while the board is moving through the assembly line. When a layer is added to the moving surface without the conveyor belt to span between adjacent feet in the direction of machine flow, the upstream edges of the feet can snag on the leading edge of the added layer. This destroys the board and can result in a complete shutdown of the assembly line to restart the line for a board of desired thickness.
Despite the development in the area machines for manufacturing corrugated boards, conventional solutions fail to provide a long-term, feasible, and cost effective solution for substantially reducing friction. Thus, a need still exists for a long lasting machine and method for manufacturing corrugated board that avoids friction related problems.
The present invention meets the needs described above in a low friction machine for manufacturing corrugated board. The invention effectively extends the life expectancy of critical machine components such as the feet used in pressure applicators as well as a conveyor belt by reducing friction. Using a check valve in the pressure applicator, the present invention expels a burst of air that hinders feet from directly contacting the sliding corrugated board. Because considerable friction results from the direct contact between the pressure applicators and sliding board, avoiding this direct contact substantially reduces friction and increases the longevity of the pressure applicators.
In another advantage, the invention allows precise control on the amount of pressure applied to the corrugated board by individual pressure applicators. As a result, operators can vary the pressure applied to the board depending on the location of the pressure applicators. For example, an operator may increase the pressure applied by pressure applicators located along the centerline of the corrugated board while decreasing the pressure exerted by pressure applicators located along the edges of the board. Because a controller that make these adjustments remotely, avoiding manual adjustments saves considerable time.
Generally described, the invention is a machine for applying pressure to a substrate positioned on a hard surface. The machine includes a foot operative for applying pressure to the substrate. The foot includes a conduit having a first end and a second end. An actuator attached to the foot and moves the foot between a raised position and a lowered position. The lowered position is proximate the substrate. An air supply connected to the first end of the conduit and supplies air to the foot. A check valve coupled to the second end of the conduit and regulates airflow in the foot. The check valve is opened when the foot is in the lowered position and closed when the foot is in the raised position.
In another embodiment, the invention is a machine for applying pressure to a moving substrate positioned on a heated surface. The machine includes a row of pressure applicators. Each pressure applicator includes a foot operative for applying pressure to the moving substrate. The foot includes a conduit having a first end and a second end. An actuator attached to the foot and moves the foot between a raised position and a lowered position. The lowered position is proximate to the moving substrate. An air supply connected to the first end of the conduit and supplies air to the foot. A check valve coupled to the second end of the conduit and regulates the airflow in the foot. The check valve is opened when the foot is in the lowered position and closed when the foot is in the raised position.
The invention includes corrugated board manufactured by the process of applying pressure to the corrugated board. The process includes applying pressure to the corrugated board with a foot. The foot includes a conduit having a first end and a second end. The process also includes moving the foot between a raised position and a lowered position with an actuator attached to the foot, wherein the lowered position is proximate to the corrugated board. The process also includes supplying air to the foot with an air supply connected to the first end of the conduit. Another step includes regulating airflow in the foot with a check valve coupled to the second end of the conduit, wherein the check valve is opened when the foot is in the lowered position and closed when the foot is in the raised position.
In view of the foregoing, it will be appreciated that the machine for manufacturing corrugated board avoids the drawbacks of prior systems. The specific techniques and structures employed by the invention to improve over the drawbacks of the prior systems and accomplish the advantages described above will become apparent from the following detailed description of the embodiments of the invention and the appended drawings and claims.